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Nothing here states they were created in the second world.

It simply says demons were sent forth. There's the 5 Elders that could very well represent the demons.

The forest god raged is in the first world text. He existed in the first world, therefore devil fruits could as well.

I think the fighter depends on your interpretation of the depiction of how the join bus work.

If you see the image as 3 fighters merging together, then there is the possibility of a brand new fighter, either involving Goku and Vegeta or not. In this interpretation, I favor Kuu, Duu, and someone else for a new fighter entirely. I've been hoping that Kuu and Duu merge and become a smart and goofy fighter.

If you see the middle body as the emerging result of the two warriors becoming one on the left, and the final product on the right.. This interpretation would favor Vegito. I ultimately think this would unlock ss4 Vegito. The resulting Vegito would still be enhanced by Neva, so Vegetas half would still receive that influence

Dosundada starts with D. If the D in people's names hasn't been revealed yet, maybe it marks them as Dosundada? We've never met one that we know of, it's shrouded in mystery, and clearly brought up for a reason. It could have been survivors of the old world carrying their bloodlines on, and the "hybrid" between worlds could be Dosundada?

Just a thought from someone who only gets to follow the story from articles nowadays